RALEIGH (AP) — The lead military prosecutor in the case against a U.S. Army general facing sexual assault charges has resigned shortly before a court martial is set to begin.

Fort Bragg spokesman Benjamin Abel said Lt. Col. William Helixon left the case last week for “personal reasons.” Base officials would provide no further explanation or comment on how that might impact the trial scheduled to start March 3.

Brig. Gen. Jeffrey A. Sinclair, 51, has pleaded not guilty to eight counts, including forcible sodomy, indecent acts and conduct unbecoming an officer. Sinclair faces life in prison if convicted on the most serious charges.

Helixon's departure comes after a pre-trial hearing in January where he appeared visibly frustrated with testimony from the female captain who is Sinclair's primary accuser. Defense lawyers say the woman perjured herself on the stand.

The married general, who was the deputy commander of the 82nd Airborne, admits he carried on a three-year affair with the junior officer under his direct command during war tours in Iraq and Afghanistan. But he denies the woman's accusations that he twice ended arguments by forcing her to perform oral sex and threatened to kill her and her parents if she ever told anyone of their illicit relationship.

The Associated Press generally does not identify those who say they were victims of sexual assault.

With the lack of any physical evidence to support the assault accusations, the success of the government's case rests largely in the woman's credibility in testifying about what she says Sinclair did to her.

Sinclair's lead defense lawyer, Rich Scheff, said that before Hexlion quit they had a conversation during which the prosecutor expressed concern about whether a jury would find the captain to be a credible witness.

“It's deplorable that the government continues to prosecute a case that rests solely on the credibility of a witness who lied to the chief prosecutor and then committed perjury in an open courtroom,” Scheff said. “Lieutenant Colonel Helixon understood that going forward on this basis would cross an ethical and professional line, and we respect him for that.”

The captain testified that on Dec. 9, shortly after what she described as a contentious meeting with prosecutors, she rediscovered an old iPhone stored in a box at her home that still contained saved text messages and voicemails from the general. After charging the phone, she testified she synced it with her computer to save photos before contacting her attorney.

However, a defense expert's examination of data military investigators later recovered from the phone suggests the captain powered up the device Nov. 24, more than two weeks before the meeting with prosecutors. She also tried to make a call and performed a number of other operations, according to the data.

The woman's immunity agreement with the Army requires her to testify truthfully. Adultery is a crime in the military.

Page 2 of 2 - Scheff said the new prosecutor assigned to the case, Lt. Col. Robert Stelle, had indicated that the woman's immunity agreement remains intact and that the case will proceed to trial.